Classifying grates are known in which the grate bars are formed as eccentric-disk rollers and in which the rollers are arranged eccentrically. With classifying grates of this type in which the grate bars are rotatably entrained or are driven, the grate bars can have a triangular configuration with arcuate sides. Grate bars are also known with concentric ribs which are uniformly spaced apart so that in all positions, uniform free openings can be provided. The drive of the grate bars can be effected by sprocket wheels and drains. In conventional classifying grates the spacing between the bars is fixed or constant and the bars cannot move relative to one another.
One of the characteristics of conventional bar grates of this type is that the breaker product to be separated can jam between the grate bars and in the grate openings. This type of jamming action can give rise to stress at the bearings of the rotational grate bars with resulting damage to the bearings and deformation of the grate bars.